AskMen has a pretty nifty article about the 5 Things You Didn't Know About Sideburns. For instance, how the facial hair style got its name:
1- Sideburns are named after a Civil War general
Ambrose Everett Burnside lived from May 23, 1824 to September 13, 1881. A Union Army general in the Civil War and later a Rhode Island politician, Burnside was well known and well liked. He wasn’t known as a good general, often getting his forces in trouble, but people forgave him because of his freaky facial hair. Two burly muttonchops grew dangerously long and connected to a handlebar mustache. Originally they became known as burnsides, but over time the syllables were switched around.